The invention relates to apparatus and methods for medical diagnostic testing. It has application, inter alia, in detecting the onsite of peritonitis, for example, during continuous ambulatory peritoneal dialysis (CAPD) and automated peritoneal dialysis (APD) procedures.
Peritoneal dialysis (PD) is a medical procedure for removing toxins from the blood that takes advantage of the semi-permeable membrane surrounding the walls of the abdomen or peritoneal cavity. During a PD procedure, a solution is introduced into the patient's abdomen, where it remains for up to several hours, removing blood toxins via osmotic transfer through that membrane. At completion of the procedure, the solution is drained from the body along with the toxins. CAPD is the manual form of this procedure, requiring that the patient manually drain fresh PD solution into, and spent PD solution out from, the peritoneum. In APD, the entire procedure is handled by automated equipment.
Peritonitis is a common complication of both CAPD and APD. Often caused by introduction of bacteria (e.g., from the tubing, connectors and other apparatus that make up the PD transfer set) to the peritoneum during dialysis, this swelling of the peritoneum can cause vomiting, abdominal tenderness and a host of other symptoms. Although responsive to antibiotics, peritonitis can end a patient's ability to stay on APD and CAPD therapies. In extreme cases, it can be be fatal.
Standard tests for peritonitis, usually conducted on occurrence of acute clinical symptoms, include the Gram stain procedure, performing a cell count on the peritoneal fluid, culturing that fluid, and/or performing a blood culture. Largely, these tests can only be done in the lab, after a patient has presented with symptoms. By that time, the peritonitis may well have set in, resulting in undue patient distress and potentially necessitating more extensive treatment.
More recently, reagent test strips have become available, making it possible for physicians or patient's themselves to perform more immediate diagnosis. However, test strips have a limited time window of utility and have generally not been successful in early stage detection.
CAPD and APD patients are typically counseled to maintain a keen eye for another symptom of peritonitis: a turbid or cloudy effluent bag. This can be late-developing, unfortunately, and is further compounded if the PD solution remains in the body for a long period before expulsion (as is the case, for example, during daytime dwells of APD patients). Detection of turbid effluent is further complicated in APD equipment with long drain lines, since patients may only see the effluent lines and not the effluent bag (where the turbidity is more readily apparent). Moreover, patients who are blind or have poor eyesight must rely on friends, family and/or caregivers to inspect the spent PD fluid for turbidity.
The prior art suggests that such cloudiness might be detected automatically, e.g., within APD equipment, by detecting the overall amount of non-coherent, polychromatic light that passes through a vessel of PD effluent by use of a source of such light positioned on one side of the vessel and a detector positioned at an opposing side. Implementations of this technique have generally not proven reliable because of poor signal-to-noise.
An object of the invention is to provide improved methods and apparatus for medical diagnosis, testing and/or treatment in the home or lab.
A further object of the invention is to provide improved methods and apparatus for PD therapy.
A still further object of the invention is to provide improved methods and apparatus for detecting the onset of peritonitis, e.g., in connection with peritoneal dialysis.
Yet a still further object of the invention is to provide such methods and apparatus as can be implemented at reasonable cost, yet, produce efficacious results.